Toxoplasmosis is an infection by a tiny parasite (Toxoplasma gondii) that can live inside the cells of humans and animals, especially cats and farm animals.

If you have been pregnant, you may already know it's important to avoid toxoplasmosis, which people can develop by cleaning the litter box of an infected cat or eating undercooked meat or other contaminated foods.

The Centers for Disease Control and Preventing (CDC) estimates that about 60 million people in the United States could have toxoplasmosis, but most won't have symptoms because their immune systems are strong.

How It Spreads

People can catch toxoplasmosis from:

touching or coming into contact with infected cat feces (poop). A cat can become infected from eating infected rodents, birds, or other small animals.

eating raw or undercooked meat (especially lamb, pork, and venison) from animals that were infected

eating raw, unwashed fruits or vegetables that have touched manure

being born with it (a woman who gets toxoplasmosis while pregnant may pass the parasite to her unborn child through the bloodstream)

accidentally ingesting (swallowing) the eggs of the parasite, which can get on the hands after handling soil without gloves or handling uncooked, unwashed foods

drinking contaminated water

Although infection doesn't normally spread from person to person except through pregnancy, in rare instances toxoplasmosis can contaminate blood transfusions and organs donated for transplantation.

Signs and Symptoms

Toxoplasmosis is passed from animals to humans, sometimes without causing any symptoms. When kids do have symptoms, they vary depending on a child's age and the immune system's response to the infection. (Both humans and infected cats often don't show any signs of a toxoplasmosis infection.)

Congenital Toxoplasmosis

When a pregnant woman (even one with no symptoms) catches toxoplasmosis during pregnancy and it's not treated, there's a chance that she could pass the infection to her developing fetus. Babies infected during their mother's first trimester tend to have the most severe symptoms.

A woman who got toxoplasmosis before getting pregnant usually won't pass the infection to the baby — this is because she (and, therefore, her baby) will have built up immunity to the infection. Toxoplasmosis can be reactivated, meaning it can come back, in a pregnant woman who's had a previous toxoplasma infection and has a weakened immune system. Generally, it's probably a good idea to wait to try to get pregnant until at least 6 months after a toxoplasmosis infection.

Up to 90% of children born with congenital toxoplasmosis have no symptoms early in infancy, but a large percentage will show signs of infection months to years later. Premature newborns and very small newborns show clear signs of infection at birth or shortly after.

Signs and symptoms, if they happen, can include:

fever

swollen glands (lymph nodes)

jaundice (yellowed skin and eyes caused by high levels of the liver chemical bilirubin)

Toxoplasmosis in Kids With Weakened Immune Systems

Kids whose immune systems are weakened (for example, by AIDS, cancer, or medicines taken after organ transplants) are at special risk for severe toxoplasmosis infections. Especially in children with AIDS, toxoplasmosis can attack the brain and nervous system, causing toxoplasmic encephalitis (an inflammation of the brain) with symptoms that include:

fever

seizures

headache

psychosis (a type of severe mental illness)

problems with vision, speech, movement, or thinking

Duration

Although toxoplasmosis parasites may grow and multiply within a week of entering a person's body, it may be weeks or months before symptoms of infection appear (if they appear at all).

Once someone becomes infected with toxoplasmosis, the infection remains in the body for life, usually in a latent (inactive) form that won't cause side effects or harm. The infection can be reactivated, however, if the immune system becomes compromised by an HIV infection or cancer therapy.

In a child with a healthy immune system, mild symptoms of toxoplasmosis (such as swollen glands) usually pass within a few months, even without medical treatment. But kids born with severe congenital toxoplasmosis may have permanent vision problems or mental retardation. And in a child with a weakened immune system, toxoplasmosis can be fatal.

Diagnosis

More often, doctors order blood tests to measure the level of antibodies (substances that are part of the body's defensive immune reaction) produced to fight the parasites.

Genetic tests can identify the DNA-containing genes of toxoplasmosis parasites once they've invaded the body. These tests are especially useful for checking the amniotic fluid for evidence of congenital toxoplasmosis in a fetus. Obstetricians may use ultrasounds to help diagnose congenital toxoplasmosis. But these tests aren't 100% accurate and can lead to false-positive results, meaning there may not actually be an infection.

For babies, doctors ask the mother about things like exposure to household cats or contaminated food or water sources. Tests that might be done for these babies include eye, ear, and nervous system examinations, spinal fluid analysis, and imaging of the head to look for changes in the brain.

Treatment

Unless someone has a weakened immune system or is pregnant, there's often no need to treat a toxoplasmosis infection — symptoms (such as swollen glands) usually go away on their own in a few weeks or months. However, kids should always be checked by a doctor because swollen glands can be a sign of other illnesses.

If a pregnant woman gets infected, her doctor and an infectious disease specialist work together to create a treatment plan. Research has shown that treating the mother can help make the infant’s disease less severe, but it won't necessarily prevent the infant from getting toxoplasmosis.

Children born with congenital toxoplasmosis are treated with different combinations of anti-toxoplasmosis medications, usually for 1 year after birth. A specialist will decide which medicines to use and for how long.

In healthy older kids who develop serious toxoplasmosis infections, treatment usually lasts 4 to 6 weeks (or for at least 2 weeks after symptoms are gone). Kids with weakened immune systems often need to be hospitalized when they develop toxoplasmosis, and those with AIDS may need to take anti-toxoplasmosis medication for life.

When to Call the Doctor

Call your doctor right away if your child develops symptoms of toxoplasmosis and any of the following:

is already being treated for AIDS or cancer

has a condition that affects the immune system

has been taking medicines that weaken the immune system

Also call the doctor if you are concerned that your otherwise healthy child may be sick with symptoms of toxoplasmosis.

If you're pregnant, call your doctor right away if you notice even one swollen gland, especially if you've been exposed to cats or have eaten raw or undercooked meat.

Prevention

If your cat is kept indoors and never fed raw or undercooked meat, then your family's feline probably has a low risk of catching or spreading toxoplasmosis. Still, you can also catch it from eating raw meats or uncooked produce that's contaminated.

Freeze meat for a few days before cooking it, which helps to reduce the likelihood of toxoplasmosis infection, says the CDC.

Never wash raw chicken. Washing raw meat and poultry can spread germs around the kitchen. Germs are killed during cooking when chicken reaches an internal temperature of 165°F (74°C). So washing doesn't help.

Thoroughly wash all cutting boards, utensils, and kitchen surfaces (especially those that come into contact with raw meat) with hot soapy water after each use.

Cook all meats completely (the juices should be clear and there should be no pink areas).

Cat Tips

If you're pregnant, have someone else change your cat's litter box daily. And ask that he or she use detergent and hot water to clean it, then wash his or her hands after changing the litter. If you are unable to have someone else change the litter box, wear gloves when you do it and wash your hands thoroughly afterward.

Keep your cat inside at all times to keep your pet from getting toxoplasmosis from the soil and/or small infected animals it tries to catch or eat.

Keep your child's outdoor sandbox covered, especially overnight, to prevent wandering cats from using it as a litter box.

Don't feed your cat raw meat.

Steer clear of stray cats.

Don't take in a new cat if you're pregnant.

General and Household Tips

Wear gloves when gardening and wash your hands afterward.

Use window screens to try to keep your home bug-free (cat feces are a favorite haunt of flies and cockroaches and the bugs can spread the feces, and the toxoplasmosis, onto food).